Reconstruction and electronic structure of solid surfaces: Na/Ge(111), InSb(111), and Li-Al(110)

Abstract

1. Reconstructions and Electronic Properties of Alkali-metal adsorbed on Ge(111) Surface Upon adsorption of alkali-metals on a semiconductor surface, various changes occur in atomic and electronic structures of the surface. The electronic properties of Na overlayers on Ge(111) are investigated using the techniques of ultraviolet photoemission spectroscopy and photoemission of adsorbed Xenon. Adsorption of Na atoms on Ge(111)-c(2×8) and Na/Ge(111)-3×1 surfaces does not change the semiconducting surface property. The local work function measurement shows that there are two different sites in (3×1) surface. One is close to Na atoms and its local work function is 0.48 eV lower than that of the other site. This Na-induced short range interacting area is about 33% of total surface, which indicates that the Na coverage of the (3×1) phase is about 1/3 ML. The electronic structure of Na/Ge(111)-3×1 surface was also investigated by valence-band and core-level photoemission spectroscopy with Synchrotron radiation light source. The two-dimensional energy band dispersion of the surface Brillouin zone along $\overline{M}-\overline{\Gamma}-\overline{K}$ was mapped out. The surface states consist of a distinct Na-Ge bonding state and a probable \pi-chained state. The core-level analysis of the Ge 3d for the (3×1) surface presents that there are two surface components of which binding energies and intensity ratio largely changed from that of the clean surface upon Na adsorption. A comparison with other Na-adsorbed Ge(111) surfaces shows that the Na-Ge bonding in (3×1) is more or less covalent and its surface Fermi-level is close to the valence band maximum. 2. Electronic Structure of InSb(111)-$2 \times 2$ Surface The electronic band structure of InSb(111) along Γ-Δ-L(111) direction was determined using angle-resolved photoemission spectroscopy for the photon energy between 9 and 39 eV via synchrotron radiation. The bulk band dispersion is in agreement with earlier theoretic...